Cockelty Pie (Ulster)

Not as elaborate as the Welsh version, the Ulster Cockelty Pie is an easy to prepare comfort food staple.
4 dozen cockles
2 Tbsp. fresh parsley, chopped
2 Tbsp. butter
½ cup celery, chopped (100 g)
1 onion, finely grated
2 Tbsp. all-purpose flour, unbleached
2 pts (4 cups) cockle stock (1.2 L)
1 pt (2 cups) milk (600 mL)
sea salt
black pepper, freshly ground
1 lemon, freshly juiced
1 recipe Shortcrust Pastry Dough
Preheat the oven to 350°F (180°C/160°C fan, Gas Mark 4).
Scrub the cockles well to get rid of any sand and grit. Then put them into a large saucepan with preferably sea water or salt water to cover. When the water is brought to the boil and the shells have opened up, do not continue cooking.
Remove shells from the liquid to cool and when cool enough to handle remove cockles out of their shells.
Melt the butter in a saucepan, stir in the flour, then add the strained cockle juice and milk, stirring continually until it is smoothly blended. Add the chopped parsley, celery, onion and seasoning and cook for 10 minutes.
Add the cockles and lemon juice, put in a shallow pie tin or bakeware, then cover with short-crust pastry.
Bake for 30 minutes and serve hot.